1. Field of the Invention
The present invention relates generally to wavelength selective switches. More particularly, the present invention is directed to a symmetric wavelength selective switch for connecting two wavelength division multiplexing (WDM) rings.
2. Technical Background
Communication networks increasingly rely upon optical fiber for high-speed, low-cost transmission. Optical fibers were originally envisioned as an optical replacement for electronic transmission media, such as high-speed coaxial cable and lower-speed twisted-pair cable. However, even high-speed optical fibers are limited by the electronics at the transmitting and receiving ends, generally rated at a few gigabits per second, although 40 Gbit/s systems have been prototyped. Such high-speed electronic systems are expensive and still do not fully exploit the inherent bandwidth of fiber-optic systems. On the other hand, communication networks comprised of only optical components offer many intrinsic advantages over systems that use electronics within any part of the principal transmission path.
Wavelength division multiplexing (WDM) is pervasive in optical communication systems. Generally, wavelength division multiplexing (WDM) electronically impresses different data signals upon different carrier frequencies, all of which are carried by a single optical fiber. Recent research and development has suggested that an all-optical network can be constructed having switching nodes that can switch the separate WDM channels (carrier frequencies) in different directions without the necessity of converting the optical signals to electronic signals.
A wavelength selective cross-connect optical switch for selectively switching wavelength channels between two optical signals is disclosed in U.S. patent application Ser. No. 09/458,560, filed Dec. 9, 1999, entitled xe2x80x9cWavelength Selective Cross-Connect Switch (WSXC) Using a Micro-Electro Mechanical Shutter (MEMS) Arrayxe2x80x9d. A general depiction of the type in the ""560 application is illustrated in FIG. 1 of the drawings. The WSXC optical switch 10 includes two dispersive elements 12 and 14, where each dispersive element 12, 14 receives an optical input signal and disperses it into a plurality of wavelength-separated input channels, and a MEMS array 16 receiving the plurality of wavelength-separated input channels from each of the dispersive elements 12, 14 and operative for selectively switching one or more of the wavelength-separated input channels between the optical signals. The WSXC optical switch 10 disclosed in the ""560 application is accomplished with simple optical components thereby allowing construction of a sophisticated optical network at relatively low cost. Moreover, the high-speed electronics of the optical network is confined to the system end terminals that require speeds of only the individual channels and not of the total throughput of the system.
While the features of the wavelength selective cross-connect switch disclosed in the ""560 application are useful, there is room for improvement, particularly in terms of bulk optics and the switching function. Accordingly, it is desirable to extend the functionality of presently known wavelength selective cross-connect switches beyond a 2xc3x972 switch without adding additional bulk optics.
In accordance with the teachings of the present invention, a symmetric optical switch for selectively switching wavelength channels between a plurality of optical inputs is disclosed. The symmetric optical switch includes two dispersive elements receiving optical input signals from respective optical fibers where the optical input signals are dispersed into a plurality of wavelength-separated input channels. The symmetric optical switch also includes a plurality of circulators disposed on each of the optical fibers and a switching array mechanism that receives the plurality of wavelength-separated input channels from each of the dispersive elements. The switching array mechanism simultaneously switches one or more pairs of the wavelength-separated input channels between the plurality of optical inputs. Each of the circulators disposed on the optical fibers operate with the shutter array for forming an eight port device so as to independently switch wavelength channels.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various features and embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.